1. Field of the Invention
The present invention relates to a transmission lever unit for vehicle (defined as a transmission lever unit in a broad sense, including a lever mechanism for switching between xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d and xe2x80x9c2WDxe2x80x9d and xe2x80x9c4WDxe2x80x9d for operating a transmission (defined as a transmission in a broad sense, including a mechanism for switching between xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d and between xe2x80x9c2WDxe2x80x9d and xe2x80x9c4WDxe2x80x9d) of a vehicle such as a three-wheeled or four-wheeled utility (working) vehicle, a three-wheeled or four-wheeled leisure vehicle (hereinafter referred to as a small vehicle) enabling the operation by a driver seated on a driver""s seat that is apart from the transmission, and a mounting structure of a coil spring suitable for use in the transmission lever unit.
2. Description of the Related Art
In the case of small vehicles, e.g., all-terrain vehicles including leisure and utility vehicles, a transmission has gear trains for a plurality of different systems, e.g., a gear train for changing a gear ratio (high-speed gear and low-speed gear), a gear train for switching between xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d, and a gear train for switching between xe2x80x9c2WDxe2x80x9d and xe2x80x9c4WDxe2x80x9d.
In conventional all-terrain vehicles, operation levers are provided in the vicinity of a driver""s seat for the respective gear trains for the plurality of systems.
When the operation levers are thus provided, the constitution around the driver""s seat is complicated and the transmission lever unit for vehicle is correspondingly complicated.
Under the circumstances, Publication of Unexamined Patent Application No. Hei. 8-337131 discloses an operation lever unit in which the use of one operation lever enables the operations of connecting means, e.g., push-pull cables and connecting rods, for two systems.
This operation lever unit is constituted such that, while shifting operation for one of the systems is conducted by using one of the connecting means, the connecting means in the other system is free. In other words, while the switching operation between xe2x80x9cforwardxe2x80x9d and xe2x80x9creversexe2x80x9d is being performed, the force of this operation does not act to maintain the current condition (e.g., high-speed gear) of the system for changing the gear ratio. Accordingly, it is necessary to increase a detent force of the operation lever unit for the purpose of maintaining the current condition of the gear train for the system which should not be operated. In that case, however, the lever needs to be operated by a force exceeding the detent force, so that a great force is required to operate the lever. As a result, operation of the operation lever feels heavy to the operator. In addition, in this constitution, high rigidity and precision are needed in respective members. This results in a heavyweight and expensive lever unit.
The present invention addresses the above-described conditions, and an object of the present invention is to provide a lightweight transmission lever unit for a vehicle that can be operated without an increase in an operation force and need not increase the rigidity of respective members. Another object of the present invention is to provide a mounting structure of a coil spring suitable for use in the transmission lever unit.
According to the present invention, there is provided a transmission lever unit for vehicle comprising: a single transmission lever for operating the transmission unit; a first lever member swingable around a first pivot and having a second pivot; and a second lever member integrally attached to a base end portion of the transmission lever and swingable around the second pivot orthogonal to the first pivot, the transmission lever unit being adapted to select a desired combination of gear trains of first and second systems of the transmission through independent connecting means of the first and second systems by operation of the transmission lever, wherein the first connecting means is adapted to operate by a swing operation of the transmission lever around the first pivot, and the second connecting means is adapted to operate by swing operation of the transmission lever around the second pivot.
In accordance with the transmission lever unit so constituted, the gear trains of the two systems can be independently operated by using one transmission (or operation) lever, and the shifting operation for one of the gear trains does not affect the shifting operation of the other gear train. Therefore, it is not necessary to increase an operation force applied to the operation lever and increase the rigidity of the respective members. This results in a lightweight transmission lever unit for a vehicle. More specifically, the operation lever is swung around the first pivot to cause the first connecting means to operate, thereby operating the first gear train of the transmission, while the operation lever is swung around the second pivot to cause the second connecting means to operate, thereby operating the other gear train of the transmission. So, during the swing operation around either the first pivot or the second pivot, the position of the other pivot side can be maintained as it is. Therefore, it is not necessary to provide a detent mechanism with a large detent force for maintaining the current condition on the first pivot side and the second pivot side. The use of this lever unit can reduce the operation force exerted by the operator for swinging the target side. As a result, it is not necessary to increase the rigidity of the respective members of the transmission lever unit for a vehicle, and a lever unit that could be lightweight and manufactured at a low cost is achieved. In addition, the swing operation around the second pivot does not affect the swing operation around the first pivot.
It is preferable that in the transmission lever unit for a vehicle, the second pivot is provided at a tip end of the first lever member, because this provides rational placement.
It is preferable that the transmission lever unit for a vehicle further comprises a third lever member swingable around a third pivot provided in a unit frame in parallel with the second pivot, the third lever member and the second lever member being connected by means of a connecting member, and the second connecting means is adapted to operate via the third lever member by swing operation of the operation lever around the second pivot. Thereby, the tip end of the second connecting means can be easily positioned in the vicinity of the first pivot and the second connecting means is hardly affected by the swing operation around the first pivot.
It is preferable that in the transmission lever unit for a vehicle, a tip end portion of the first connecting means is connected to a portion of the first lever member that is apart from the first pivot and a tip end portion of the second connecting means is connected to a portion of the third lever member that is apart from the third pivot. Thereby, the constitution enabling the shifting operation is attained.
It is preferable that in the transmission lever unit for a vehicle, the connecting member is comprised of a rigid member, and connecting elements having three degrees of freedom are respectively disposed at a connected portion of the connecting member and the third lever member and at a connected portion of the connecting member and the second member. Thereby, the third lever member is hardly affected by the swing operation of the first lever member around the first pivot.
It is preferable that in the transmission lever unit for a vehicle, the connecting elements are a ball-joint mechanism. Thereby, the power can be smoothly transmitted with three degrees of freedom.
It is preferable that in the transmission lever unit for a vehicle, the first pivot is provided substantially vertically and the second pivot is substantially horizontal.
It is preferable that in the transmission lever unit for a vehicle, at least one of the first lever member, the second lever member, and the third lever member, is comprised of two members coupled to each other by means of elastic means. Thereby, shocking force caused by the transmitting operation is alleviated by the elastic means, to and therefore, the operator can smoothly operate the lever.
It is preferable that in the transmission lever unit for a vehicle, the first system is a system for changing a gear ratio and the second system is a system for switching between forward and reverse.
It is preferable that in the transmission lever unit for a vehicle, at least one of the first lever member, the second member, and the third lever member includes a first plate member and a second plate member respectively provided with openings overlapping with each other as seen from one direction, and the elastic means is formed by disposing a spring in the openings. Thereby, sufficient elastic function is obtained with a simple constitution and a lightweight constitution is obtained.
It is preferable that in the transmission lever unit for a vehicle, the openings of the first plate member and the second plate member have substantially equal length. This constitution allows the deformation of the entire spring, e.g., the entire coil spring to be fully utilized for elastic function.
It is preferable that in the transmission lever unit for a vehicle, the spring is a coil spring, a convex portion for prevention of disengagement of the spring toward an opposite side of the second plate member is provided at a portion of the opening of the first plate member so as to extend toward the opposite side of the second plate member and a convex portion for prevention of disengagement of the spring toward an opposite side of the first plate member is provided at a portion of the opening of the second plate member so as to extend toward the opposite side of the first plate member. Thereby, the coil spring can be reliably held in the openings.
It is preferable that the convex portion is formed by two opposed bent portions.
It is preferable that in the transmission lever unit, the coil spring is held from its outer periphery by the convex portions provided at the openings of the first plate member and the second plate member. Thereby, the coil spring can be reliably and stably held in the openings from its outer periphery.
According to the present invention, there is also provided a mounting structure of a coil spring held by two members disposed such that at least part of the members are substantially parallel to each other, for elastically connecting the two members via the coil spring, the structure having openings at parts of the members which are substantially parallel to each other so as to overlap with each other as seen from one direction, and the coil spring disposed in the openings.
In accordance with the mounting structure of the coil spring, it is possible to realize the mounting structure of the coil spring capable of holding the coil spring simply and reliably by the two members that are substantially parallel to each other.
It is preferable that in the mounting structure of the coil spring, the two members are first and second plate members, the openings of the first plate member and the second plate member have substantially equal length, a convex portion for prevention of disengagement of the spring toward an opposite side of the second plate member is provided at a portion of the opening of the first plate member, so as to extend toward the opposite side of the second plate member and a convex portion for prevention of disengagement of the spring toward an opposite side of the first plate member is provided at a portion of the opening of the second plate member, so as to extend toward the opposite side of the first plate member. In this mounting structure, the coil spring can be reliably held in the openings in a simple manner.
It is preferable that in the mounting structure of a coil spring, the coil spring is held from its outer periphery by the convex portions provided at the openings of the first plate member and the second plate member. The coil spring can be reliably and stably held in the openings from its outer periphery.
It is preferable that in the mounting structure of a coil spring, the openings and the convex portions are formed by one pressing operation. Thereby, these portions can be formed speedily and at a low cost.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.